An image forming apparatus such as copying machine, printer, facsimile, printing machine, and multi-functional apparatus may produce an image by transferring a visible image (e.g., toner image) from an image carrier to a recording sheet.
Such visible image (e.g., toner image) may be fixed on a recording sheet by applying heat and pressure to the recording sheet when the recording sheet passes through a fixing unit.
Such fixing unit may employ a heat roller type or a belt fixing type as heat applying method, for example.
The heat roller type may include a heating roller having a heat source (e.g., halogen lamp) and a pressure roller contactable to the heating roller, wherein heating roller and the pressure roller may form a fixing nip therebetween.
The belt fixing type may include a belt as heat applying member, wherein the belt may have a heat capacitance smaller than a roller.
Further, a fixing unit may employ an electromagnetic induction heating method as heat applying method.
In such electromagnetic induction heating method, a heating roller may include an induction coil therein. When an electric current is applied to the induction coil, an eddy current may be induced in the heating roller with an effect of magnetic field generated by the induction coil, by which the heating roller may be heated.
Such configuration may not need a preheating process for the heating roller, which may be conducted for conventional heat roller type. Accordingly, such electromagnetic induction heating method may preferably increase a temperature of the heating roller to a given temperature instantaneously.